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How to determine the direction of rotation of components inside a gas turbine engine using the blade profile?
I am new to Gas turbine Engines.
As of now,I am trying to understand the gas turbine engine DGEN 380 by the manufacturer Price Induction.
So I have identified the components such as Intake fan,Planetary gearbox, Centrifugal Compressor,HP and LP turbine.
However,I am not sure of identifying the correct direction of rotation for each of these rotating components based on blade profile. So if someone could explain it in a simple way,I shall be thankful.
https://minijets.org/fr/300-500/price-induction-dgen-380-390/

I'm not sure about the other parts, but the intake fan runs clockwise when looking into it from the front.

Possible duplicate of How does the fan in the jet engine suck in air while the engine is stationary?

@ Ron Beyer  I agree, and the turbine wheel seems to turn counterclockwise, also seen from the front of the unit. That's probably because of the planetary gearbox...

@RonBeyer can you tell me how the direction is related to the blade profile for the intake fan?

Take a look at the fan, and imagine it spinning. It has to grab air and force it backwards, so the "scoop" part grabs the air and pushes it in. It works the same way a desk fan or computer fan does, get one of those and spin it to see what direction the air moves.

If you know the direction of gas flow, you can determine the direction of rotation of axial flow components (like the fan and turbine in the example) by the angle of attack of the blades. Think of it intuitively--if you were to blow air through the engine in the same direction it flows during operation, which way would the blades windmill? The direction of windmilling is the same as the direction of powered operation, as long as the airflow is in the same direction.
Because their angle of attack, of the blades of the fan would deflect air flowing into the engine counterclockwise when viewed from the front, meaning the fan rotates clockwise when viewed from the front (or counterclockwise from the rear looking forward, which is the conventional way of expressing rotation).

For this particular engine, all other turbomechanical components rotate in the opposite direction as the fan, indicating that the low pressure shaft is connected to the fan using a gearbox that reverses the rotation direction.
This is the low pressure turbine and shaft:

The compressor rotates in the same direction as the high and low pressure turbines, and is attached directly to the high pressure turbine shaft with no gearbox. The high pressure turbine is axial flow and looks like a smaller version of the low pressure turbine, but the compressor is not an axial flow component, which makes the analysis slightly different.
Unlike in axial flow components, in radial flow components like this compressor (a synonym for a radial flow compressor is a centrifugal compressor), the airflow enters and exits in a different direction. The direction of flow also differs between energy-absorbing (turbine) and energy-dissipating (compressor) components. Gas enters radial flow turbines at the edge and flows inward, exiting at the center. In radial flow compressors, gas enters at the center and exits at the edge. You can determine the direction of rotation by imagining the forces the air would exert as it changes direction, similar to the windmilling axial flow components:


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Why does the Pressure ratio across the compressor increases when the mass flow rate is reduced?
I am learning about Rotating stall in Axial Flow Compressors. So, when we throttle the compressor then there is Pressure Rise and later after the peak pressure rise tip stall starts to appear.
But I am trying to figure out the relation between mass flow rate and pressure rise.

The simplest way to understand this is to refer to Bernoulli's Theorem.  When the flow of a compressible fluid (in this case air) speeds up, the density of the compressible fluid goes down (and vice versa).  Pressure is directly related to density, so pressure also goes down when flow rate (velocity) goes up.
Mathematically, Bernoulli's Theorem is expressed $\rho \times v =$ constant.
Here, $\rho$ is density, $v$ is velocity.
Look at a diagram of a Venturi tube, and it will make sense.

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Why the lift and drag coefficients for the simulations differ from the experimental value?
I am doing CFD simulations for NACA Airfoil 2415 using K-Omega SST model on ANSYS fluent. I am using an tetrahedral unstructured mesh with 20 Inflation layers on the wall. I have been comparing my result with the experimental data found in NACA 460 report. What I notice is that the values which I get using simulations are higher in comparison to the experimental data. The Reynolds number for which I am simulating is 3 million. Any reasons why the difference is?
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091108.pdf

Small differences between the simulation and the reality are to be expected. How big is the difference you observe?

As an example for 10 degrees AOA, the experimental Cd is around 0.02 while I am getting around 0.06 with the CFD Model. The difference is small at lower angle of attacks and the differences get large with high AOA.

@Ashish Tiwari Is it possible, based on higher differences at higher AOA, that your simulator is calculating induced and parasite drag, while the NASA is only counting induced drag?  Are they both using infinite AR (limited AR would include wing tip drag, which increases with higher AOA).  I would check if raw data generation was "on the same page"

Is the error also linear with $\alpha$? I would start by trying to isolate the source of the disparity.

It may help to post your results (and comparison against the NACA sectional data) and the turbulence model parameters you're using.

@robert digiovanni Its a 2D condition with infinite A. R..so it's just the parasitic drag. But I am not sure of how to relate it with laminar turbulent transition. Transition is not captured in   the turbulence model that I use. While there are three distinct phases in the growth of boundary layer experimentally.

If it is 2D infinite, then it might be INDUCED drag only.  Your results make more sense. If no programming differences are discovered, I would try to find wind tunnel data matching the chord and airspeed of your programming. Since Reynolds is a combination of both, you may wish to tighten your parameters a bit.  BTY, the NACA report is from 1935.

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How does the critical Angle of attack changes with Increasing Reynolds Number?
I am simulating NACA 2415 Airfoil for different Reynolds Number i.e. 2 million,3 million and 4 million on ANSYS Fluent. The difference between the critical Angle of attack is quite vast. For the 4 million Re number, I am getting a critical Angle of attack close to 46 degrees which seems to be very weird and looks incorrect to me.
Any explaination of how different the critical Angle of attacks would be for the above mentioned Reynolds Number?

There are two different questions in here: CFD stall prediction and Reynolds number effect. What turbulence model are you using?

Hi, I am using k omega sst. I got a good result for Reynolds number of 3 million. I am using a unstructured mesh for it. But for 4 million and Reynolds number differing by a million atleast, I am getting poor results when it comes to critical angle of attack

Try to improve your boundary layer mesh. As you already pointed out, 46 deg stall AOA is certainly not right. I'm surprised it even converged. Reynolds number does delay flow separation, but not nearly to that extent.


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Why apply resolutons in data words for ARINC 429 bus
Data words transported over the ARINC 429 bus are defined and built-in units, ranges, refresh rates, number of significant bits, and resolution.
Why is it necessary to include resolution? Does resolution really have any significant impact on the signal? I think resolution is just a mere step size for the signal, so why use incremental resolutions, like 0.0000000002? Does this small incremental really make a difference in the data word?

Not sure if i understand your question correctly. Do you ask why it is necessary to define a resolution? If you have a limited number of bits which have to encode certain range of data, you will have a limited resolution.

The resolution tells you what value to assign to your LSB of the received value

@selectstriker2 why is that important?  How does that impact the signal?

It doesn't affect the signal, it helps decode the data in the 32 bit word

@selectstriker2 Thanks -- you last 2 comments are helpful.

The ARINC 429 Word resolution tells you what value the LSB corresponds to. You can also tell what the resolution should be by looking at the Range and Significant Bits.
It doesn't describe the actual electrical signal.


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Why is the S-duct intake on the Tu-154 uniquely oblong?
Is there an advantage to the oval/elliptical shape of the Tu-154's S-duct intake? It appears to be taller and an overall different shape than the side-mounted cowlings.

This doesn't appear to be a feature common to trijets or even on those with S-ducts.

EDIT: Upon further research, it appears the 727-100 had an oblong intake (Thanks Terry!), and the Hawker Siddeley Trident had an entirely unique shape. So my original premise of the Tu-154 being "unique" no longer holds. I am still curious about the implications of the different designs.

So I tried looking up some 727 photos to compare, and it looks to me like this photo has an oblong intake: http://warbirdsnews.com/wp-content/uploads/727finalflight-678x381.png while this one does not: https://www.deltamuseum.org/images/site/history-aircraft/boeing-727/boeing_727_ca_late_1990s.jpg which seems odd?

The 727-100 had an oval duct and the 727-200 had a round duct.

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.
AIRLINERS magazine Sept/Oct 99 edition:
"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."

That's definitely a step in the right direction! On an unrelated note, I love that VP-BAP is one of the few privately owned 727s still operating in the US.

The vertical fin is tall and thin, so it makes sense that an inlet/duct mounted in the fin and configured for optimum streamlining might not be perfectly round.


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How much of a plane is replaced over the lifetime of an aircraft?
A photo of an OC-135 with (presumably) P&W TF33-P-5 engines made me wonder how many of the components had been replaced, and what was left of the original airframe, engines, and other parts. There are many aircraft operated today that are at least 50 years old (no real significance to that particular number).
Over the lifetime of say, a C-135/707 airframe without engine upgrades, is any of the original engine left? Are body panels replaced? Landing gear? Control surfaces?

The B-52 is also interesting given it's extremely long life.

My 1973 Cessna is 46 years old this year. All the structural aluminum and steel parts are all original.    Brakes, inner tubes, tires, those are normal wear items.  Engine cylinders when they developed cracks, opted to replace with less crack cylinders.  Propeller blades, also a wear item. Misc. engine accessory bits too. Avionics were upgraded twice by me since 1996.  Last year I replaced all the external ABS plastic fairings with new fiberglass parts. And it's finishing its 2nd ever paint job and a new front window.  Many small planes get similar treatments, and undergo annual inspections.

Control surfaces can be replaced if they get beat up badly from hail, ground vehicle, etc.  Wings can be patched - damaged part is unriveted, new one riveted on (plane at my airport hit a deer on landing late at night and needed part of wing reskinned).  Ultimately, almost anything is repairable if one wants to spend the money. Another plane had corrosion found in the wing - so the owner went out and got another wing.  A wing for a 4-seater is less than a military plane, but there are plenty to choose from out in the 'boneyard' if one is needed.

A nice nod at the Ship of Theseus paradox: https://en.wikipedia.org/wiki/Ship_of_Theseus

@CrossRoads and many see much more. Was in Canada last year where someone was reskinning a Gypsy Moth, replaced the main wing spar, tension wires, brakes, tyres, propellor, control cables.

That depends on how the aircraft is used, and how much its flown. Most aircraft parts that are life-limited are cycled out either after a certain number of hours, or after a certain number of cycles (takeoff to landing is one cycle). Years is a somewhat irrelevant term in aviation since it does not practically measure much more than the time that has elapsed since it rolled off the assembly line.
If a plane is privately owned, and/or lightly used and there are no AD's against any of the parts causing them to be replaced there may very well be old planes flying around with old parts. With that in mind, heavy use, commercial planes that get banged around, hit by birds etc may have some new body panels, fresh landing gear, updated avionics etc.
In your specific example, body panels will be replaced if they are damaged but provided there is no corrosion or damage and the airframe is within its cycle/hour lifetime nothing will be replaced. The same goes for the landing gear (although tires may be cycled faster than other parts).
According to this article, the JT4, which some 707s had, has a 2400 hour TBO. While TBO is not a legal limit you can bet that most commercial operations are going to pull them around there. Its possible an engine gets overhauled and replaced on the same airframe thus there may be planes flying around with their original engines. However most engines can only be overhauled so many times and in 50 years, considering regular usage, its likely the original engines are long gone.
There are even some rare 100-year-old early era airplanes still flying that likely have original parts due to the lack of availability of any replacements.

TBO is a legal limit for all commercial op i.e. part 121/135 etc, it is not binding for privately operated aircraft. However, some commercial operators are able to show special circumstances and receive a waiver. The flight school I got my PPL in 1975 had a Cessna Cardinal with a 2200hr TBO that was being flown with more than 2400hrs as a complex checkout. The school was allowed to operate it so long as either it was only flown in the pattern or there was a flight instructor on-board.

The number of years since the plane rolled off the assembly line is by no means irrelevant - corrosion doesn't care whether the plane's flying or not.

In the US an aircraft may be allowed to fly indefinitely so long as it continues to meet the requirements of the definition for "Airworthy" in Court Order 8130 (.2e par 9).

Note: Aircraft operated by government agencies or the military do not
  have to comply with any rules, laws, or regulations - they may operate
  in any manner the agency desires (as long as they are not used for paying passengers). These aircraft are described in FAR 1.1 as "Public Aircraft". Examples: military fighters and transport, firefighting, research, etc.

There are two possible scenarios for replacing a part.
1) Life Limited: The manufacture or FAA through an AD (airworthiness directive) requires a part to be replaced at a certain limit i.e TIS (time in service) - calendar or operating hours, number of operating cycles (i.e. number of landings or pressurization cycles), etc. The manufacture is required to provide a chapter/section of the POH (Pilots Operating Manual) that list all life limited parts.
2) On Condition: Maintenance personal (often during an inspection) find the part 1) inoperative, 2) near or beyond "Service Limits" published by the manufacture, 3) in the discretion of maintenance personal worn and no-longer safe for operation, deemed not airworthy, etc. These parts are repaired or replaced as needed.
In practice many older aircraft have been completely replaced (technically a "repair"). There is no limit on the amount an aircraft can be "replaced".
War birds are one such example. It is legal to salvage an airplane from the ocean floor, use the corroded metal as a template to make new parts and completely assemble an aircraft from new material. The restored aircraft must be identical to the original aircraft and is legally considered the same aircraft ("all" the parts where repaired!).
There are many examples, such as the P-38 "Glacier Girl" being one of the more recent well document examples. It was salvaged after being crushed under 265ft of glacier ice for over 50 years.

Part 121/129 transport category aircraft have a hard life limit, thanks to the widespread fatigue damage rule in 2011.

I said, "may be allowed to fly indefinitely so long as it .. is airworthy". Part 135/121/129 opps are allowed to make their own rules subject to the approval of the FAA. Often companies like engine, prop, and Boeing set low time life limits, then get repeated amendments and extensions as fleet data becomes available. Even then a trashed 121 aircraft might be sold and used in another category such as research, firefighting, etc.

There is one part that must not be replaced: The type plate.

Oldest aircraft in the world still flying is a 1909 Bleriot belonging to the Shuttleworth Collection in the UK. Might be interesting to research if any part installed by Bleriot in 1909 remains in that one :)

@jwenting the type plate. :)

@jwzumwalt What you say was true in the past where FH and FC limits were related to the validity of the maintenance program, which was regularly extended. Maintenance is subject to the airline/regulator not the airframer. The fundamental change is WFD makes the entire fuselage a LLP, just like an engine disk. LOVs are written into regulation, which takes them out of airline discretion. If you read the article, Boeing will not support any aircraft in any service worldwide that exceeds LOV, which effectively ends its use. This is basically the same as Soviet/CIS aircraft certification.


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Why does the SR-71 Blackbird sometimes have dents in the nose?
On many pictures (maybe on most of the pictures) part of nose looks hammered or slightly smashed, or bent.
Please note these 2 symmetric dents just behind nose spike:

source

source
On other pictures these dents are missing:

source
Why? Is this a feature or damage?

You don't normally see perfectly symmetrical damage.  They look like fairings that are installed over sensors that have to be mounted in the chines, or, it was decided to put a step along the edge of the chine for an aerodynamic reason, and the shapes are transition fairings.

Good info here:https://www.flightglobal.com/pdfarchive/view/1973/1973%20-%202291.html

Micrometeorites and bits of smashed satellite?

High-speed mosquito strikes.

The SR-71 had a detachable nose (photo #2), and could change between three different nose cones depending on the mission. I haven't found a lot of information on the three, other than what this site and this site mentions:

Training nose with dead weights
Radar nose containing a Side Looking Radar. This is probably the bulge you saw on the photos.
Photo nose containing the optical bar camera, taking very wide photos of the ground.

The linked sites are good references, but they don't explain the leading edge bulges. As those links explain, the sensors are located elsewhere.

From SR-71.us: "The antenna assembly/motion sensing unit, transmitter, receiver and related equipment are installed in a specially-configured detachable nose."

TIL the mission payload is in the nose of SR71.

The dents are there to provide a proper thickness window for DEF systems.  Ferry noses had no need for DEF systems and so didn't have the bulges.  If you look carefully at the noses you will see that there is a band just aft of the pitot mast that is all composite and it was called an isolation something or other.  There were several noses.  OBC is optical bar camera and could take a horizon to horizon panoramic picture like every second - in stereo if you wanted to use twice as much film.  The SLR or side looking radar, which was replaced by the ASARS advanced synthetic aperture radar.  The Asars nose looks pregnant and is quite distinct.  Those are the operational noses of which I know.  There may have been others before my time.  There was a capre nose, but I don't know what CAPRE stands for or if that nose is distinct from the ferry nose.  The SR was originally intended to have not only swappable noses but also swappable forebodies and they would latch them at the fs 715 break.  you would have an interceptor forebody, a penetrating bomber forebody, a recon forebody, which are way cheaper than the whole proulsion system, which would be swapped out according to mission requirements
I was on the project in Burbank from 1987 to 1990

Welcome to Av.SE! Thanks for the added perspective about the nose sections, and about how so much was intended to be swappable. Hadn't come across that before, though it makes total sense. What a cool aircraft to have been involved with - can only imagine all the fascinating stories from that era.

Bjelleklang is right, the nose is detachable and would be switched out according to the mission's needs. The bulges are a key component of the (for that time) very sophisticated radar imaging system, ASARS-1. There's more information here.

As it turns out, the notches have nothing to do with the ASARS, see Haakon Dahl's answer.

The indentations have nothing to do with ASARS-1, based upon first hand knowledge.

When looking at a picture of a Blackbird, you might be looking at either of 2 different aircraft - the YF12 and the SR71. One of the differences between them is the nose - the SR71 has a smooth continuous chine, whereas the YF12 has the indentations that you've spotted but with usually a forward-looking sensor there (possibly IR?).
So it depends which aircraft you're looking at.

SR-71 and YF-12 have disdinctly differend noses, the aircraft in the pictures of this question definitely are not of an YF-12. It might be possible, even easy, to confuse SR-71 and its predecessor  A-12: https://migflug.com/jetflights/a-12_oxcart-vs-sr-71_blackbird/

Or the A-12, or the SR-71B, or a D-21 picture mistakenly labeled SR-71.

ECM receivers - put there for the more advanced ECM systems the Blackbird got in the ‘70’s and ‘80’s. Just read an article about it

Welcome to Aviation.SE! Since you read an article about it, please include a short quote from that article and a link or reference to it.

I don't have a copy with me right now, but the book Skunk Works is Ben Rich's account of taking over the Lockheed special-projects group from Kelly Johnson, and includes quite a lot of description of the SR-71 development and operation.
As I recall, he described that the SR-71 nose would often soften and deform in flight from the heat of very high speeds. I suspect that the bulges are a product of that.
As to why they are so symmetrical, I especially notice on your second picture, where the bulges appear to be propagating back from the join in sections.

If a nosecone would deform like this from heat, you'd have a serious problem.

@Mast According to this site about the SR-71 the "Temperatures ranged from 450 degrees F (232 C) near the back part of the aircraft to 950 degrees F (510 C) near the engine exhaust. The cockpit had special heat-resistant glass to withstand surface temperatures of 640 degrees F (338 C).". Dunno if that's enough to deform a nosecone. Probably not.

@PerlDuck Considering the entire thing is built to withstand that heat, yea, don't think deformation is the answer here. The other answer(s) look(s) much better.


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What makes an airplane STOL?
I watch STOL pilot champs Zenith CH701 here.

The engine power are: 130 HP, 80 HP, 120 HP and 100HP, respectively. Amazing. As per my observation, the third airplane takes off in a distance shorter than its length. It uses an 120 HP engine. I tried to search over the net how long the required runway is to make it take off. Unfortunately, I could not find it. But I believe that should be longer than its length.
What are the technical requirement to make an airplane able to STOL?

Thrust, lift and light weight.

There are a number of factors that can contribute to short take off landing (STOL) ability.
The Zenith page has some information:
http://www.zenithair.com/stolch801/design/design.html
Wing Shape
A more "cupped" wing shape generates more lift at a slower speed, enabling a shorter take off. This sacrifices the aircraft's top speed. Note that this limitation can be mitigated by making the wing shape changeable with slats and flaps.
There are other modifications that can be made to a wing shape to favor STOL characteristics. For example, there are a variety of STOL kits that can be added to existing aircraft. These range from wing tips to other airfoil shape changes.
Wind Speed
By taking off into a higher speed wind, the takeoff distance is decreased. With a strong enough headwind (and a skilled pilot), a STOL aircraft and appear to take off vertically with little or no runway needed.
Power to Weight Ratio
The more powerful the engine is compared to the weight of the overall aircraft, the less runway is required to achieve takeoff speed.

@RonBeyer - I agree that the wording is off... Will update.

Might want to add wing loading -- combine low wing loading with high lift devices and you can take off slower, hence shorter.

Also drag. High drag will slow acceleration and increase take-off run  (although in most cases high drag is a by-product of high lift, which reduces take-off run)

Thank you @RQDQ for the nice explanation.

The planes had high-lift wings - nice thick wing, and with flaperons at the trailing edge to make the wing seem wider (front to back) to create more lift.  Lightly loaded, just single passenger, and it also was quite a windy day, so they weren't depending on just engine horsepower to create airspeed over the wing - witness the 4th landing, where the plane was blown sideways and then backwards and the tail blown up in the air and up on its nose.
And of course practice.

Any plane, under any wind conditions, depends exclusively on engine power in order to generate airspeed.

Seems, pilot skill was more contributing in that champ. He can take off and landing very short. Another factor are important, but in this case, as there was another higher horse power where the design are same, so the more contributing thing is the pilot skill.

Those STOL (not VTOL) planes have wings with high-lift devices as large flaps and slats, that greatly increase the lift coefficient, thus allowing the plane to take off with relatively little airspeed.
Besides, in the video, the takeoff runs are greatly favored by a stiff headwind...

Yes my friend, apologize for the error. I have corrected it to STOL. Another comment I have to read several time to make me really understand.

I found some interesting things here: large flaps and slats, that greatly increase the lift coefficient, thus allowing the plane to take off with relatively little airspeed, and stiff headwind. I have to study them so I can comment further as they are quite new for me.


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Does the B-1B Lancer have controllable canards?

These three pictures shows the B-1B Lancer's canards and its elevators. I am not sure to call that feature a canard as the jet also has elevators. In my limited understanding, canard and elevator are substitutes, to use canard or elevator. Then my questions are:

What is that feature's name? Is that canard?
Is that feature (specific to the B-1B) also controllable like elevators?

Picture source 1 and 2: captured from this Youtube video.
Picture source 3: from here.

From Wikipedia:

The Rockwell B-1 Lancer has small canard vanes or fins on either side of the forward fuselage that form part of an active damping system that reduces aerodynamic buffeting during high-speed, low altitude flight. Such buffeting would otherwise cause crew fatigue and reduce airframe life during prolonged flights.

Having a traditional tailplane does not exclude the use of term canard, but it must be admitted that in the case of B-1B the forward control surfaces are so small in relation to other lift or control surfaces that the term "fin" might be more semantically appropriate.
B-1B Canards are moving, but not pilot controlled:

The B-1's Structural Mode Control System rotates the [canard] vanes automatically to counteract turbulence and smooth out the ride.

Wikipedia: Canard (aeronautics)
Wikipedia: Rockwell B-1 Lancer

Why couldn't they do the buffet suppression with elevators, I wonder?

Just a guess, but as the elevators, or actually stabilators on B-1 are huge, and they control both pitch and roll of the aircraft, the system might have been too slow and/or complicated for the task. Even if the stabilators were able to react quickly enough and it was possible to incorporate the damping system to them, should the damping system fail, it might seriously affect the controllability of the aircraft.

@Jpe61, what is this B-1B Canards are moving, but not pilot controlled mean? What is that mean "moving"?

@AirCraft Lover, their angle of attack is modified by the active damping system. The word "moving" might be a little misleading, sorry.

So, can I say that it (the vanes) are controlled indirectly by the pilots?

@AirCraft Lover, no, not even indirectly. The damping system has full authority. I edited the answer to make this point more clear.

But they do move, don't they?  Interesting in than now with sensors we can combine AOA measurement and response in one unit.  In other words, make the AOA sensor much more robust and moveable.  It could be set at 0 AOA (non lifting/low drag canard) and deflect only when AOA is unacceptable (for airliners)  or work as a damper (for very low altitude high IAS bombers).

Well the word "active" kinda hints they do :)

@Jpe61 From the few sources I can find online, B1 seems to have stabilizer+elevator, not stabilator. Do you have a definitive source?

Oops, I stand corrected @Jimmy. As they have the aforementioned double duty of pitch and roll control, I should have called them tailerons. Definitive source and proof of them not being stab+elev would be pretty much any youtube video showing B-1B taxiing. Such as this: https://youtu.be/6r3pPFzpzaw

Thank you @Jpe61. Nice explanation.

Tailerons is a good one!  How about televons?

@Robert DiGiovanni I'd stick with tailerons since it's a well established term ;)


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Saw this plane in documentary on the Falklands War. What type is that?
That nose reminds me of ground attackers, but I don't know why.

Looks a lot like the FMA Pucará :
https://en.wikipedia.org/wiki/FMA_IA_58_Pucar%C3%A1


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Why do we measure translational accelerations but angular velocities in an IMU aircraft?
I am wondering why we measure for attitude of an aircraft its angular rate (instead of angular acceleration) and for the translational channel the acceleration instead.
The computers can integrate both signals to get the current attitude and position of the aircraft.
In another question on this forum someone stated:
"I think that the biggest problem is that in a coordinated turn, the angular acceleration is 0 and the lateral proper acceleration is also 0, so without measuring angular rate, an IMU would be unable to distinguish a coordinated turn from straight-and-level flight! That's a critical flaw."
To my understanding: if a computer just integrates the signals you will know your attitude and position. So in order to me more precise one should use the acceleration values (and reduce the bias/Drift).
Can you help me in this?
Thank you!

After further reflection I think the intent of the question is clear enough to answer; deleting comments. If the answer isn't helpful, perhaps the question could be clarified in some way, if it is possible to do that without invalidating the answer.

Working backwards, a control input to create a turn results in constant lateral acceleration and constant rate of turn (angular).  But for applications such as aerobatic aircraft, roll axis acceleration may be just as important as (steady state) roll rate.  It depends what sensors you have and what you want your software to do.  Interesting side bar would be what hydraulicly boosted larger ailerons could do for something like a P-38.

The basic, underlying argument is that an IMU contains a linear accelerometer and angular gyroscope, because these are simple, self-contained instruments which rely on basic physics to obtain measurements. They are the simplest instruments for the job. But there are a couple of aspects which I tried to break up as follows:

Pretty much all IMUs measure the translational acceleration and angular velocity because it is easy to do so. Accelerometers and gyrometers are pretty old and also easy to construct as they hinge on basic physical principles. In contrast, measuring translational velocity and translational position or rotational position (attitude) directly, is much much harder, and in general not possible with basic physical principles (at least not in all three dimensions).
Measuring rotational acceleration is possible, but again, not as simple as measuring rotational rate. You can arrange several translational accelerometers in a special geometric figure to obtain rotational acceleration, but it is complicated and requires post-processing. There are even rotation accelerometers available for purchase. However, the much bigger problem is that you do not want to use rotation acceleration to obtain attitude. You stated that an acceleration signal can simply be integrated twice to obtain position, but every integration accumulates a bias. This is inevitable with even the most expensive gyroscopes: If you integrate the rotational velocity to obtain attitude, the attitude estimation will accumulate an error (the cheaper the gyroscope, the quicker the error accumulates). Therefore, in general you are happy that you already have rotational velocity, and do not need to obtain it by integrating rotational acceleration which would incoporate even more error.
It depends a bit on what you would like to achieve: The goal of pretty much all IMUs is to obtain an estimation of the orientation of the device. The combination of rotational velocity and translational acceleration allows you to do this with basic sensors in a self-contained package. This is ideal for a lot of applications which shall not rely on external sources such as the position of the sun, or GPS satellites for example.

As an important side note: You wrote

"I think that the biggest problem is that in a coordinated turn, the angular acceleration is 0 and the lateral proper acceleration is also 0, so without measuring angular rate, an IMU would be unable to distinguish a coordinated turn from straight-and-level flight! That's a critical flaw.

This is most definitly wrong. A coordinated turn incoporates non-zero angular rates in at least two axis. Therefore, you can most definitly distinguish a coordinated turn from straight-and-level flight with an IMU!

Here is a link to a simple, inexpensive self-contained instrument with no moving parts that measures yaw rate. The nature of piezoelectric rotation sensors is such that no integration is needed to obtain this value.  The instrument can be switched on in mid-flight--even while turning-- and will immediately provide reasonably accurate values.
How would it improve accuracy to construct an alternative type of sensor to somehow directly measure angular acceleration -- if that would even be possible-- and then integrate the acceleration values to obtain angular rate?
Similarly, if you are interested in calculating aircraft attitude, wouldn't it be better to measure angular rate and integrate once, than to measure angular acceleration and integrate twice?
The question seems to imply that there is an advantage to measuring acceleration rather than actual rate whenever possible.  This is a misconception.
The nature of piezoelectric sensors is such that it is possible to directly measure angular rate.  Unfortunately it is not possible to directly measure linear velocity-- if it were, all navigational computations would be greatly simplified.  Instead, linear acceleration is measured directly, which then must be integrated to obtain linear velocity, which must be integrated again to determine position.

Re opening link: these instruments have been built in various versions, some of which go through a calibration phase on start-up, others of which don't.  Answer would be improved by changing link to a specific version that is clearly documented not to go through any calibration phase, but I don't have that handy at present.

Additional links to various versions of same, some of which also contain a lateral linear accelerometer driving a slip-skid ball presentation: https://www.kitplanes.com/a-modern-turn-coordinator-belite/, https://generalaviationnews.com/2016/09/21/belite-introduces-electric-turn-coordinator/, https://www.flyingmag.com/experimental-manufacturer-brings-back-turn-coordinator/, https://www.airframer.com/news_story.html?release=13975.  As an aside, original units definitely measured yaw rate, not using a canted gyro axis as would an actual "turn coordinator"; can't speak definitively to latest.


text:
How does an airline respond to the loss of one of its aircraft in a hostile country?
I was wondering if the steps are the same as an accident on home ground where there is a go team and how they set up the area around the crash site, with a team contacting passegner relatives.

Hostile countries tend to be avoided and not overflown by airlines to prevent these situations from happening

@Afe This has happened before, MH17 is a perfect example. They set a restricted area over the war zone, it was proved to be inadequat,e but based on how many aircraft flew over that week you can't say that airlines avoid overflying those areas. They fly over any area that has hostilities if they are told that it is okay and a internal risk assessment says its okay.

@Bullfrog For hostile country I understand a country that is politically an enemy of the country of registration of the aircraft (i.e. at war). Malaysia was "neutral" in the conflict between Ukraine and Russia

The "country of occurrence" must protect the area and conduct an investigation. The airline is not involved directly, but "the State of Registry, the State of the Operator, the State of Design and the State of Manufacture have the right to appoint an accredited representative to participate in the investigation.". You may read all details in this BEA summarization of texts relevant to accidents.

In MH17 accident mentioned in comments, Ukraine was the "State of occurrence", ICAO was associated to the investigation officially and UK AAIB analyzed the recorders after they were released by rebels. As for contacting relatives, this is done by the operator which knows who was on-board (the list has to be provided to investigators within 2 hours), operators are prepared to such occurrence and have procedures. States with fatalities can also participate to the investigation.

Situations like this have happend, most recently was MH17 which was shot down over the Ukraine, many airlines up until then were flying over Ukraine with a minimum altitude applied to flights transiting (FL320). And many flights also flew over that week:

Aeroflot - 86 flights
Singapore Airlines - 75 flights
Ukraine International Airlines - 62 flights
Lufthansa - 56 flights
Malaysia Airlines -  48 flights

I am using how MH17 was handeled to answer this question. However, it should be noted that no two situations are the same and the way they handled this situation may never be used again.
The area of the accident still had hostilities and was not held by the Ukraine government, who would traditionally secure the scene and invesitigate. This was held by Donetsk People's Republic, considered by the Ukrainians and moajority of the world as rebels.
Access to the area had to be negotiated and even though the got assurances of access and safety this was given and revoked at various times based on the war. Other problems that occured was the issue of the site being looted. Beacuse it couldn't be secured by investigators there where personal belongings and potential evidence removed.
In the end the black boxes where handed in and examined to have been not tampered with. In the end it was an international team of investigators that examined the site as the Ukraine's investigators where not trusted by the Donetsk People's Republic.
The biggest part of this investigation was negotitiation with multiple parties. Some of who may have caused the crash. That becomes the dificult nature of investigations in a war zone.
What happens at home to the victims families doesn't change.

Thank you so much


text:
How does drone reliance on GPS make it 'semi-stealthy'?
I saw this on CNN today.

For months, US intelligence and military personnel in Iraq have been raising alarms about the risk to American forces from these newer, more sophisticated Iranian-made drones. Rather than being guided by a pilot from a remote location, some of these small, fixed-wing drones use GPS navigation, making them far less visible to US surveillance systems and impervious to jamming.

I understand how an independent guidance system is probably jam-proof, but how  does using GPS make the drones less visible? Don't all military drones rely on  GPS?

Assuming that CNN knows what they're talking about with regard to aviation and military matters is, increasingly, a hit-or-miss proposition. Many of their "journalists" report on things without even considering the (considerable) depths of their own ignorance.

Assuming that anything said on CNN, or any TV news outlet, is even vaguely coherent is a mistake !

The key bit is: "far less visible to US surveillance systems" - those systems 'look' for Infra-Red and Radio signals, rather than just what the human eye can see.

"impervious to jamming" Even for CNN that's some pretty incorrect information.

It’s a rare news article that gets anything right about aviation.

For being remotely controlled, drones need to emit and receive a radio signal. If the outgoing signal contains a video feed, it will be high bandwidth and be like a beacon announcing the location of the drone. By pre-programming the flight path and using GPS location fixes, the drone will be passive and not emit radio signals.
Before GPS, high precision navigation needed an active radar system which would scan the surrounding terrain and compare the results with an onboard map. Such navigation systems were used by cruise missiles but, by relying on an actively emitted signal, would announce their presence to suitably tuned receivers.
While it is true that such a passive drone cannot be jammed, it is still possible to spoof the GPS signal or to jam the GPS signal itself, leaving the drone navigation system only with dead reckoning in the vicinity of its target. Also, when no communication with the drone is possible, it will only follow a pre-programmed pattern and not be able to respond intelligently to a changed situation. Such spoofing has been demonstrated by the Iranians in 2011 when they diverted a US drone officially flying over Afghanistan and when misleading tankers in the strait of Hormuz recently.
Not all drones rely on GPS since there are alternatives (GLONASS, BeiDou or NavIC), apart from active systems like Terrain Contour Matching (TERCOM).

Inertial navigation is probably also a good alternative (especially when worried about interference), but I'm not sure if that is actually used in drones.

@Bianfable Inertial navigation is the basis of dead reckoning but becomes progressively unreliable with time due to drift. It needs a GPS fix now and then to eliminate drift.

@Bianfable I would think that yes, because the 1 Hz refresh rate of GPS with random jitter around current position is insufficient for the flight control system so it needs the gyroscopes and accelerometers anyway, but the accuracy won't be good enough for the final targeting.

@JanHudec there's nothing inherently 1Hz about GPS or any GNSS system, and many receivers offer between 5 and 20 updates per second.

@Bianfable Older cruise missiles did indeed use inertial navigation. Some were accurate enough to hug the terrain and fly between mountains and hills (indeed some even used the terrain to correct for INS drift). The thing is to get accurate INS is hard.. really hard. But to build something with GPS guidance is easy. I can buy a $40 GPS module today and write a simple Arduino code to fly something to some location over a weekend.

Spoofing GPS is still easily detected with INS. And even when GPS is spoofed, it needs to be spoofed in a rather specific way, or else it still can be used to correct for INS errors.

@MSalters For detecting spoofing, your software must anticipate it. The RQ-170 back in 2011 did certainly not. Next, once spoofing is detected, who do you trust? Your INS will still drift and make the navigation unreliable. Once the spoofed signal drones out the real one, you have no GNSS signal you can trust.

@slebetman Make sure your GPS module doesn't shut itself off because it thinks you're making a cruise missile :)

So the answer is that's it's not really specific to GPS or GNSSes (a drone using VOR beacons would have the same issue), but it's that a drone with a programmed course is less visible than one with constant communication with a controller.

@user253751 My government is more likely to shut me down than the GPS module. It has happened before: https://en.wikipedia.org/wiki/Bruce_Simpson_(blogger)#DIY_Cruise_Missile

@slebetman Depends how many missiles you build

@user253751 For xjet/RCModelReviews that number was 1. But he was advertising doing it mainly for the purpose of getting his government to take the threat of DIY missiles seriously (which he both succeeded and failed - the NZ government tried to stop him but to this day there is no law or task force or even a plan to handle a situation of someone building a DIY missile)

@PeterKämpf or a star shot using a sextant. Not sure if equipment for that exists that's small and light weight enough to fit inside a small to medium sized drone.

@jwenting yes, on a cloudless day and in still air. I could list all methods but then run the risk of oodles of comments telling me that this is not answering the question. So I decided to stick with GPS and its consequences only.


text:
What is the altitude record for the F/A-18 Hornet?
Does anyone know how high (above MSL) the F/A-18 ever went? Its service ceiling is 50,000 ft, but when going up steeply, is it able to surpass 100,000 ft altitude?

Would possibly need to be going very very fast as it hit 50,000ft because I would image the engines flaming out .. check out the air-density at 50000 vs 100000ft - it's 1 order of magnitude lower at 100kft, and its about 1/80th of the density of 5000ft - https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html

SR71 had a ~80,000ft MSL (as a comparison) [or it could be 90k - depends on the source].

@MrR Yes, you have to do that in steps. I'm flying my Hornet to around 40,000 ft at first, there I remain in horizontal flight until I reach ~1050 knots, then I rise again to ~50,000 ft, do the same, then to ~64,000 ft from where I slowly descend to ~60,000 ft to reach about 1050 knots (you can't gain that speed at 64,000 ft in horizontal flight anymore). When I reach a fast enough speed I sharply pitch the nose up. This is how you reach peak altitudes in the F-18. My current altitude record so far is 92,800 ft (more than 28 km) but I fly on unlimited fuel. Takes patience to reach the speeds.

@Giovanni What simulator is that?

Hmm - are you sure the simulator is that good (i.e. takes into account the thinness of the air and it's impact on engine power, lift, etc.)

@MD88Fan Microsoft Flight Simulator X. It's the Steam Edition from 2012.

@MrR Yes, I have not good control above 80-90,000 ft, I have to push the yoke harder for pitch down. And as I said, my Hornet is unable to reach 1050 kn in leveled flight at 64,000 ft. But it's able to reach 11 50 kn at 20,000 ft so it does take the thinnes of air into account of course. How much realism is set is also important, maybe at maximum realism this wouldn't be possible even with unlimited fuel.

Not sure about the F/A-18, but during tests in the 1960s the F-104 went up to 103,389 feet officially, and around 120,000 feet unofficially (Wikipedia). The Hornet has a better thrust/weight ratio than the F-104, so I'd assume that people have been above 50.000 feet with it as well.

@bjelleklang Why are Smith's flights considered unofficial records?

I don't have the referenced books so I can't say for sure. Best guess is that it was documented, but not in the manner specified by the FAI for the record to be approved.

I can tell you my experience during my stay in Zaragoza Air Base in northeastern Spain, in 1998. After heavy maintenance work, the twin-seater was ready to fly. In order to check all work done, we did a parabolic flight in clean configuration (no loads under wings or fuselage). It was a flight test so we decided to push the limits a little and see the real capability of the General Electric F404 engine. After acceleration and trying to maintain the best angle, we were able to climb up to 63,000 ft.
It was quite difficult to fly the plane when crossing 45 or 48 thousands (I don't remember well), so we decided to connect the auto-pilot. The auto-pilot can handle the plane easily at those altitudes with such low air density.
I recall the last portion of the climb was a nice parabolic trajectory in zero-g (you cannot imagine how dirty the cockpit was, I could see a pencil and some screws from maintenance floating in front of me, among some other things) until we regained positive g's in the descent. It was an interesting flight, but as stated by others, not practical at all from the combat viewpoint.

Were you flying an F/A-18D?

@rclocher3 It was an EF-18/B (E for 'España'). After major upgrade work the aircraft was significantly modernised becoming EF-18BM. It was updated by EADS CASA. The local designation is C.15, for both the air-to-air and air-to-ground roles.

You will need to have a chat with maintenance about FOD after that flight.

There are reasons why a Hornet would NOT go above its 50,000 feet service ceiling. Has it been done in testing? Probably. Has it happened accidentally? Probably. But there’s no reason to do so. Aircraft performance is pretty bad at the service ceiling, so BFM/ACM isn’t going to go well. Turn performance and speed will be very negatively impacted. Dropping bombs isn’t a great plan either- a heavily loaded jet might not even make it that high.
Then comes the issue of the pilot. It’s unlikely that the Hornet’s life support system would work that high. Even if it could, depressurization would kill the pilot, because there's no space for a pressure suit, nor the infrastructure to support one.
Given all this, it’s just not practical to fly above the service ceiling.

Evidence that the cockpit's too small for a pressure suit would make this answer a proper frame challenge.

The Hornet, like all high-altitude jets, is a pressurized plane. I guess it creates the atmosphere from 10,000 ft altitude in its cockpit, why would that fail when going to SR-71 altitudes and higher?

One reason why would be to intercept the Soviet/Russian MiG-25 which was flown to altitudes more than 118,000 ft by Aleksandr Fedotov. But one should really keep the reason why to the pilot.

@CamilleGoudeseune I think most of your edits to this answer were unnecessary. Especially the first sentence you could have beleft.

@Giovanni; keep in mind that the MiG-25 never flew to 118kft on operational missions, this was only done in testing. Chances are that it was low on fuel and with no additional payload, so even if it could do so regularly it wouldn't really achieve anything....

@bjelleklang Well, I wonder if the F/A-18 could to the same. Probably not, because it's not that fast (Mach 1.9 maximum in leveled flight). Fedotov in the MiG-25 achieved a new altitude record for jet planes, for non-rocket wing aircraft, and for a ground-launched plane. Not to mention the fact that he went to outer space in a jet but he was not the first pilot to do so as discussed above (Smith in the F-104 was).

I have been to 55,000’ in a back seat pax ride off the east coast of Australia in an F/A-18B. The jet had two wing tanks on and had no troubles at all getting there. Pilot said we could go higher but needed pressure suits in the event of a depressurisation occurring.


text:
Can electricity be harvested from magnets in jet engines?
I was reading about bleedless-787 power system but found out it still requires a gearbox.
What if you put coils around the "tube" part of the jet and tiny magnets in the end of the fan/compressor blades, this would generate an electric current that could be useful for powering the aircraft's electrical systems. With the right control system, it could perhaps also be used for precise corrections for vibrations/rpms resulting in better reliability and higher efficiency. Finally, it might be useful to assist the startup process by spinning the blades from 0 to some initial speed (ideally, replacing the starter mechanism but thats probably a stretch).
I know jet blades are subject to extreme mechanical and thermal stresses, so implanting a ferromagnet is probably not possible. But given the tremendous angular velocities, it probably doesn't require much magnetic material to induce a useful current. Perhaps a chemical spray deposition would suffice.
Has such a system been considered before? Are there any other obvious reasons this wouldn't work? Obviously there's no free lunch, and this system would steal angular momentum from the fan blades and require more fuel. But if it could somehow replace the generator and/or starter, it would yield tremendous weight savings.

The need for a gear box is to stabilize the shaft rpm. Aviation electricity is AC of a fixed frequency. If airplanes used DC system like a car, or have chosen to use a inverter to stabilize the frequency like a home gasoline home generator, then you could certainly skip the gear box.

So you propose replacing a relatively compact generator with a generator many times the size (you'd have to put stator coils all around the fan or the LP compressor). How exactly do you imagine this could save weight?

@TooTea: I have never seen the generator on a turbofan, so I dont know how much either would weigh. But I believe fewer moving/contacting parts is generally preferred in any mechanical design, however.

@tootea watt for watt, the mass would be the same.  Mass of aluminum is decided by V x A.  Mass of iron is decided by VA / frequency.

"tiny magnets in the end of the fan/compressor blades" even if very tiny, they are going to a marked increase in the momentum of inertia of the fan ---> bad. The aerospace industry is trying to make the blades as light as possible because of that, not because of the weight itself

The currie point of iron is roughly 1000C. The operating temperature of a typical turbofan is closer to 2000C. No, you aren't going to be able to keep magnets in a jet engine.

The power generation method you propose is used on almost all motorcycle and small lawnmower engines: magnets pressed into the rim of the flywheel, with stationary coils nearby in which current is induced to flow.
These motors run at speeds much slower than the fan disc speeds in a turbine engine, so stuffing the flywheel rim with magnets does not compromise its structural integrity the way it would in a highly-stressed fan disc.

...Moreover, a the whole point of a flywheel is having a large moment of inertia. If it didn't have the magnets, it would have to have an equivalent amount of ballast mass. Very different story with turbine blades!

Today's commercial jet engines can reach temperatures as high as 1,700 degrees Celsius (that's 3,092 degrees Fahrenheit) (see here).
Every magnet type has a specific Curie temperature above which its magnetic properties are lost forever; the most resistant is cobalt, whose Curie temperature is 1,130 Celsius, so any permanent magnet inside a jet engine will quickly become a lump of non-magnetic metal.
A different option, currently under investigation, is to use the temperature difference between the inside and outside of the jet engine to generate current, via the thermoelectric effect.

Welcome to Av.SE! The temperatures you mention are at the hottest part of the engine, inside the combustion chambers. The tips of the fan and compressor  blades, where the OP suggests putting the magnets, don't get nearly as hot as that, since they're upstream of where fuel is added to the compressed air.

@RalphJ Yes, that is true, but the demagnetisation curve still creates an issue. As long as the temperature isn't even there will be an unbalanced load added by the magnets. Even worse, the pull and the imbalance could change dynamically depending on the season, microclimate, the flight phase, the flight leg and the time of day.

I totally agree that magnets on the end of the finely balanced fan blades would be extremely problematic for all sorts of reasons. My comment was simply to highlight that temperatures upstream of the combustion chambers are nothing like those inside or just past them.

To be specific, this is the Seebeck Effect

Another case of yes, but why would you want to? The starter generator assemblies on most jet engines does the same thing at far less weight and complexity.

Can electricity be harvested from magnets in jet engines?

Yes, it could be. There would certainly be engineering challenges to overcome in order for it to be a stable design, but it would be possible.
The main reason it's not done was raised in the comments by @user3528438. Expanding on that a little bit: generating power in this manner will result in AC current, which is what the plane uses, but the frequency will be dependent on the speed of the rotors. Since the rotor RPM changes throughout flight the frequency of the AC current generated will change, which is not good for the airplane's electronics. Hence why there is a gearbox to regulate RPM to the right level for the airplane's electronics to work properly.

Some modern aircraft actually use variable frequency AC power. See e.g. How does the A350/380 operate on Variable Frequency AC generators?


text:
Will the new Boeing NMA be 'more electric' than the current B787?
I understand that the B787 is the 'most electric' aircraft to date, however there have been many issues with the plane, and I'm interested in knowing if the latest Boeing New Midsize Aircraft (NMA) - possibly the B797 - will still use the same 'more electric aircraft' architecture as a result.
Specifically, are there any details/guesses on the following:

If the electrical power generation capacity of the Boeing NMA will be lower/higher than the B787
If the Boeing NMA will 'revert' back to traditional bleed-air engine systems.
If the Boeing NMA will use more or less electric components (such as in actuation systems) than the B787.

Any help on any one of the questions would be very appreciated!

Have they announced the 797? It would help to know what plane we're talking about - the NMA or something else.

Oops sorry I meant the new Boeing NMA

Do you have a reference to the 'many issues with the plane', the B787?

As far as I know none of the variable frequency generators, the electrical pressurization, or electrical actuators were issues to the contrary they gave full satisfaction and reduced fuel consumption. The issues were with the lithium batteries, the single piece composite body, the fuel leaks, and logistic provisions from numerous manufacturers outside the group. So there is no reason to return to conventional bleed, non electrical actuators, constant frequency generators etc. Of course the lithium batteries are a problem, but now in case of fire it is limited to a containment.


text:
What is the cause of cracking and corrosion in Trent 1000 engines?
According to this description and this one of some Trent 1000 engine problems, there appears to be a problem with cracking/corrosion of the fan blades, but does anyone have any insight as to why this is the case? (And why this problem doesn't occur on other platforms?)
I was thinking it could be due to the composites used in the compressor fan blades, or perhaps something to do with the no bleed-air system unique to the Trent 1000, but I'm not entirely sure.

Possible duplicate of What causes this much engine damage?

Your formulation assumes this engine have more problems than other types. Although this might be true, it looks like astroturfing, and calls for opinion based answers. You should rephrase your question. Sonething like "what cause corrosion damages on jet engines?" Illustrated by this specific example.

The problem is sulfidation corrosion, according to this article:
https://airinsight.com/rolls-royce-trent-1000-corrosion-issues/
Turbine blades are made of metal, and they suffer temperatures and forces so high that they are usually 'grown' from a single metal christal. A single blade can cost as much as a luxury car.
The problems also seem to be related. Corrosion leaves a little pit, which turns in to a crack due to the cyclic loads.


text:
What is the purpose of extending one degree of flaps (perhaps with spoilers)?
What would be the use of one degree of flaps? And is there any reason to use both flaps and spoilers combined?

Related: Why do slats deploy first?

.....how can you not know the answer?  You’re God!

Normally, one degree of flaps in fact only translates to an extension of the leading edge devices (e.g. slats), trailing edge flaps remain fully retracted.
On some aircraft this configuration can be used for take-off.
Combination of flaps and spoiler is for example used in slow flight on steep descends. The flaps ensure that the wing doesn't stall, the spoilers dump part of the lift and act as airbrakes to keep the speed under control.

As mentioned in other answer, you use the flaps to put the wings in a configuration where, at the cost of more drag, they increase lift; this allows the aircraft to fly a bit slower.
The spoilers, on the other hand, are used as a temporary measure to decrease lift and increase descent. So, basically, in approach you would have your flaps in a fixed position, and eventually would use the spoilers for a short time to adjust the glide path (i.e, "I'm coming too high").

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What is the correct ATC phraseology in the US for an immediate - no delay takeoff?
Just wondering - what's the correct ATC phraseology for a takeoff where a plane does not stop first after lining up with the runway centerline before starting their takeoff roll?

Redwood five-two-six-three, runway three-zero cleared for takeoff, no delay.
Redwood five-two-six-three, runway three-zero cleared for immediate takeoff.

Just got one yesterday. Not sure of the exact wording but I think it was.  Cherokee N9999 cleared for takeoff Runway 29, Cessna on 1 mile final. no delay.

Assuming US/FAA:
The Pilot/Controller Glossary only has one instance of "no delay":

MINIMUM FUEL
  −
   Indicates that an aircraft’s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not
  an  emergency  situation  but  merely  indicates  an emergency  situation  is  possible  should  any  undue delay occur.

"Immediate takeoff" doesn't exist, either, but we do get

IMMEDIATELY − Used by ATC or pilots when such action compliance is required to avoid an imminent situation.

We can cross-reference this with the Skybrary entry for Immediate Takeoff:

When given the instruction ‘cleared for immediate takeoff’, the pilot is expected to act as follows:

At the holding point: taxi immediately on to the runway and begin a rolling take off without stopping the aircraft. If it is not possible to begin taxiing onto the runway at once or if take off performance calculations mean that a standing start is necessary, then the clearance must be declined
If already lined-up on the runway: commence take-off without any delay. If this is not possible for any reason, the pilot must advise the controller immediately.

So that suggests that "immediate takeoff" is more standard. My experience has always had the clearance be "no delays".
If the P/CG doesn't technically define either phrase then I can suppose that they use "no delays" to avoid the knee-jerk "I must do something" to "immediately".  For "no delays" you can always easily respond "unable" and wait until the next plane lands.

I have heard both, with the "immediate takeoff" probably being a little more frequent.

According to the ICAO Doc 4444 14th ed. (Procedures for
Air Navigation Services - Air Traffic Management )
They mention a clearance for "immediate take-off" in section 7.8.3.4:

7.8.3.4
In the interest of expediting traffic, a clearance
for immediate take-off may be issued to an aircraft before it
enters the runway. On acceptance of such clearance the aircraft
shall taxi out to the runway and take off in one continuous
movement.

I don't see any reference to "take-off, no delay" or "cleared for immediate take-off" in the FAA ORDER JO 7110.65W (air traffic control procedures and phraseology).
I believe both are correct with ATC opting to use "Cleared for take-off, no delay." to shorten their transmission to save time.

Phraseology is a PROCEDURE, so, we should follow what is written on manuals. ‘Cleared for immediate takeoff’ is the right way to say.

Here's one from the field,

TOWER: Southwest 3828, Midway tower, runway 31C, line up and wait. Don't plan on stopping.
SWA3828: 31C line up and wait, Southwest 3828.
TOWER: Southwest 3828, traffic holding in position on the crossed runway, traffic on 3-mile final for the crossed runway, no delay please.  Turn left heading 250, Runway 31C, cleared for takeoff.  The wind 060 at 9.
SWA3828 and DELTA1328: Heterodyne

What follows the heterodyne is what makes this one famous, but the answer to your question as plays out here, is the controller intentionally used informal language in his advisory "don't plan on stopping" and the admonishment "no delay please".

Thanks, a real world example. Is the "turn left heading 250" an instruction for after takeoff?

@jeff0000 yes, the controller was really putting a lot of message in a few words because he didn't want the time delay of 3828 stopping motion and restarting...

There's also the option of expedite.

EXPEDITE− Used by ATC when prompt compliance is required to avoid the development of an imminent situation.

https://www.faa.gov/air_traffic/publications/media/pcg_4-03-14.pdf


text:
Why do NY ARTCC Standard Operation Procedures have different altitude limits than the NY Class B airspace?
The NY Class B airspace is defined, officially, as seen in this document, which can be found in the VFR Class B Graphics in the FAA website. In this graphic (and in the corresponding shapefile, Class Airspace), the flight altitude limits can clearly be seen, for example 70/30 in the "outer ring", meaning, below 7000 FT and above 3000 FT.
However, in the specific SOP definitions for the NYARTCC, here, different altitude limits can clearly be seen, for example in the DEP 4L LAND 4L/R.
Why are these two limits incompatible? Which ones are technically "officially" valid?

The information from the FAA will the the official values. The SOP information is for simulation only, not real world use.

Thank you for your answer. Could you provide a link regarding to the aforementioned SOP information? Using the FAA provided Class B data (the corresponding shapefile from here (ais-faa.opendata.arcgis.com/) ), there is only information up to 7,000 feet. What about the airspace above that? Where can I find this information?

I'm not sure where to find more info but you can post the FAA shape file data as an answer to your previous question, if you found what you were looking for.

It may not be obvious to someone reading this question casually but the NYARTCC site you linked to is run by virtual aviation enthusiasts for the VATSIM network. So I'm not sure what sort of answer you expect, because you're comparing two completely different things. As for the airspace above 7000', it's class E.

Indeed, I found out in the disclaimer at the bottom of the page. In fact, I may have not phrased my question very well. My confusion arose because the NY TRACON is divided into sectors (as I see in various software such as EuroScope), and I have found that these sectors have quite different flight levels. The various SID/STAR procedures around the major NY airports also make reference to much different altitudes than those in Class B. I better post a different, clearer question. When I clear up what is going on, I will return to provide an answer here.

The commenters have a good point that the SOP documents you liked are for hobbyist simulation and are not necessarily faithful reproductions of real-world procedures. But even in the real world who owns which specific volume of the air at which specific altitudes is not necessarily correlated with the regulatory airspace class for a given volume of air at a given altitude.
The two altitude limits are different (not "incompatible"!):

One is regulatory, and binding on pilots. No pilot may operate in the Class B airspace, unless they have received a clearance from ATC allowing them to do so. For IFR aircraft, they will receive their clearance on the ground; they will be cleared to fly a certain route at a certain altitude, and it does not matter what airspace class the route crosses or enters, because they have already received a clearance to fly that route. For VFR pilots, they may operate as they wish in Class E airspace, but before entering Class B airspace must receive a clearance from ATC telling them which heading to fly at what altitude. (There are similar but less restrictive requirements that VFR aircraft must abide by to enter Class C or Class D airspace.)
The other is not regulatory, and has to do with ATC. Regardless of the airspace classification of any volume of air, one and only one specific control position is responsible for all aircraft operating within that volume. The document you found lays out the boundaries (in 3D space) for those volumes of air, which are not directly relevant or known to pilots. The volumes will be designed so that certain activities (arrivals joining the localizer and coming in to land, or departures climbing away from the airport) can be monitored and controlled by only one controller without unnecessary handoffs.

Related: https://aviation.stackexchange.com/a/56045/34686 .  A brief condensation of the letter posted in this answer might be as follows: "The control tower only 'owns' the Class D airspace, not the E4 "extensions". Thus the tower can only grant SVFR privileges in the Class D airspace, not the E4 'extensions'. The regulatory aspects are a different 'kettle of fish" from the 'ownership' of the airspace, but we believe that the regulations are also such the SVFR is never permitted in surface-level Class E 'extensions' (E4 airspace) (ctd) –

(Ctd) "The regulatory aspects are a different 'kettle of fish" from the 'ownership' of the airspace, but we believe that the regulations are also such that SVFR is never permitted in surface-level Class E 'extensions' (E4 airspace) regardless of who owns it." That last point, by the way, is probably not consistent with the original intent of the FAA at the time the relevant rules were drafted, or the best possible interpretation of the rules as they stand today, or even with the majority of current ATC practice regarding the surface-level Class E "extensions" (E4 airspace)--for more, see (ctd)

(Ctd) for more, see https://aviation.stackexchange.com/questions/64202/in-actual-practice-do-artc-center-personnel-generally-follow-the-rule-that-a-sv/64204#64204 , https://aviation.stackexchange.com/questions/64246/what-are-the-historical-precedents-of-todays-e2-and-e4-airspace-us/64247#64247 , https://aviation.stackexchange.com/questions/74738/what-indication-has-the-faa-given-that-phrases-like-surface-area-of-class-e-air , https://aviation.stackexchange.com/questions/74738/what-indication-has-the-faa-given-that-phrases-like-surface-area-of-class-e-air/75022#75022

Airspace class is not the same as airspace ownership.
TRACONs own a larger (often far, far larger) chunk of airspace, both horizontally and vertically, than is designated class B/C/TRSA. You can see rough maps of airspace owned by TRACONs in the answers to this question. Unfortunately, exact dimensions are not published anywhere by the FAA, so all we have are these maps (created for another purpose) that have leaked.
Everything in between and above the TRACONs is owned by the ARTCCs.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What if I fail to receive FAA Medical Certificate via mail?
My AME just called to let me know that my FAA Class 3 medical certificate had been issued and was sent to me via airmail from United States to China. Since April 7th, 2014 when it was dispatched, it has been over 2 months now and I still don't receive the certificate.
I called local postal office and was told I needed to find a 13-digits tracking number (e.g. AB123456789CD, 13 digits, with 2 alphabetic letters at the beginning and end of the string and 9 digits in between) of the mail so they could check for me. The problem is I don't have it and I have no idea where to find it on the https://medxpress.faa.gov website.
Can anyone help me on how I can get this number? What are my options should I fail to get ahold of the certificate?

I disagree with the close vote due to not aviation related. IMO it is most certainly related to aviation. It may be too narrow, however. I would recommend rewording it along the lines of "I haven't received X yet, which is required to fly/attend flight school, now what can I do?"

You're really asking a postal service question (and from my experience with the postal service you're probably out of luck, even if you had the tracking number: Unfortunately when the USPS hands packages off to other nations' postal services that's often the last tracking update - either the item gets to its recipient or not, but it's gone into a black hole).
In any case the answer to the aviation/FAA half of the question ("I haven't gotten my new medical certificate yet - what do I do now?") is much simpler, and involves more helpful people than international mail: "Contact the Medical Certification branch" (see here).
In this particular case you want to actually call them on the phone and speak to a human being to determine (a) if they have a tracking number, and (b) how to proceed to ensure that you have a valid medical certificate in your possession.
I know in cases like this the Medical Certification branch can also fax you a copy of the certificate (I believe these are valid for 60 days) while you try to get things straightened out and get the actual paper certificate in your hands.

Thanks a lot for the help. I phoned them by the numbers here and the staff helped me by sending an electronic copy to my email and telling me to print it myself. I asked if the printed copy would hold the same validity as a mailed certificate and she said yes. Is this true? I mean this is way more easier but I'm not sure if I can really use this printed copy to attend a US aviation school? What's the difference between a printed electronic copy and a mailed certificate?

@kavoir.com Please accept the answer above if it satisfies you, plus your additional question(s) might make an excellent second question.


text:
Can you fly an airplane at a 90° roll angle without losing altitude?
I've seen this answer to the question about flying upside-down, but tilted by 90°, there should be no surface creating lift (except maybe the vertical stabilizer).

The vertical creates a significant downforce in knife-edge flight, so the rest of the airframe has to create even more lift than what is needed to carry its weight.

No, but you can fly it at a 270° roll angle. /Shows himself the door...

Given the right engine size anything can flight

Indeed. All that is needed is a max TWR >= 1.

the video link does not work

It depends. As always. If thrust is high enough, why not?
Knife edge flight is a regular part of aerobatic performances, and the fuselage is producing almost* all the needed lift. This requires

Enough speed,
A low ratio of aircraft mass to fuselage side area, and
Enough rudder deflection to trim the aircraft in a sufficiently high sidelip angle.

For horizontal flight your installed thrust must be sufficient to compensate for the high drag in this attitude. This should be no problem with powerful propeller aircraft if their fuel system keeps them supplied at this attitude. Jets must make sure that the sideslip angle can be tolerated by the intake.

The smoke from the exhaust indicates that this biplane flies horizontally. Yes, it is a large model airplane (not man-carrying, but almost big enough for that). But the laws of physics don't change with scale. For an example of a full-size aircraft doing a knife edge, see this video. Thanks go to @romkyns for pointing this out to me!
Note the rudder deflection to keep it at this angle of sideslip. Direction is controlled with the elevator. At this rate of sideslip the propeller thrust contributes to overall lift as well, however, the vertical adds a substantial downforce in order to trim the aircraft and the fuselage has to supply the remaining lift.
* Almost means that the propeller will carry some of the weight, but the large downforce on the vertical needs to be compensated, too. In sum, the lift contributed by the fuselage is very close to the weight of the plane.

That's a large scale unmanned aircraft in the photo. It operates just like a full scale aircraft but has less weight. That particular plane has enough power to hover on the propeller. I fly these regularly, and you can sustain knife-edge for the whole flight, but the propeller is providing the all lift, the fuse and wings really don't.

@Jasmine: no, that's a real airplane flown by a real human.

http://www.flyinggiants.com/ is a model aircraft web site (I'm a member there - jasmine2501). Sometimes they do post full scale photos there, but the large planes we fly these days can not really be distinguished from the full scale versions on looks alone. This very well could be a model of Skip's plane. The point is still the same though - on planes like this the engine is providing all the lift and the fuselage is relatively not involved.

@Jasmine Here's a photo of from Skip Stewart's own website of his plane in the same attitude: http://www.prometheusbiplane.com/wp-content/uploads/2014/07/Scott_Slocum_Ribbincur_SNF102.jpg

@Jasmine: The remark about the propeller creating lift is correct, I added it to my answer. But without fuselage lift the plane could not keep that attitude.

What do you mean? The fuse really doesn't contribute when we do the high alpha maneuvers with RC stuff. You can see that in the designs of them - the best models have almost no fuselage at all, to improve airflow over the surfaces in high alpha. When you're hovering the plane, the only airspeed you get over the surfaces is from prop wash. It's a bizzare way to fly but it works.

If you wish to include this in your answer, I've found a video of a full-sized biplane performing a perfect knife-edge. I think it illustrates that this is very much possible better than anything else.

@romkyns Sadly, that link is now broken. Any chance you know of a still-working link to that video?

I'm not sure if it's the same video or not, but this video shows Stewart in knife-edge flight (along with several other things.)

the video link does not work

@PeterKämpf , fascinating and I appreciate the craft is "flying" horizontally (the vector of motion is horizontal -- see smoke).  In the other question I was asking about the aircraft "being" horizontal while flying (at 90° roll)

re "Jasmine: no, that's a real airplane flown by a real human."-- rc fliers are real humans too!

@Fattie Thank you for letting me know. YouTube is a poor platform to link to. I replaced the link with one of an F-16 doing a knife-edge pass. Most videos show model airplanes and many airshow videos have very amateurish camera work, so it is hard to find a decent replacement.

Regular airplanes, no. They depend on lift produced by the wings and fuselage to stay airborne. No aircraft that I know of can produce enough lift with its component tilted 90°.
This all assumes 'normal' airplanes though. If you have enough thrust, there's nothing that says you need to depend on wings for lift, and if your thrust is vectored at least a little downwards producing enough of a vertical component to keep you from descending, it won't matter which direction anything else is pointing. The extreme example of this is of course space rockets.

If you fly fast enough and with the nose high enough, almost any airplane fuselage would produce enough lift to maintain level flight... assuming it doesn't break apart first. As Peter's answer points out, this maneuver is performed commonly in aerobatic aircraft. The downward component of the thrust does help, but it's not nearly sufficient on its own to maintain level flight in most aircraft (jet fighters do commonly have thrust/weight ratios > 1, but most other aircraft don't.)

Quite a few planes can do it. Among the more popular ones at airshows are the Pitts Special and Extra 300. The Su27 jet fighter have also been known to do this.

This happens (for several seconds at a time) as part of the "hesitation roll" aerobatic maneuver.
It depends on the fuselage alone for lift (in excess of the vertical component of thrust), so the nose has to point into the sky and the rudder is used to maintain that attitude. Because fuselages have rather dismal L/D it will require sufficient thrust, or bleed off a lot of speed.

Well, it's not quite the fuselage alone is it? Doesn't some of the lift also come from the thrust (i.e. sin(pitch) * thrust)? The fuselage does provide the vast majority of it in most situations, though.

@reirab: You're right, and the vertical stabilizer also contributes some, unless it needs to be killed by the rudder (which would depend on where the aerodynamic center of the fuselage in sideslip is located relative to the CoG).

During "normal" flight with wings level, the amount of lift generated will vary with the wings angle of attack (alpha). Within the normal flying envelope of the aircraft, the relationship between lift and alpha will be nearly linear.
In an ideal situation, with symmetric airfoil and not considering fuselage/slipstream effects, at zero degrees alpha, no lift will be generated.
There sideslip angle of the aircraft is normally called beta. In normal straight and level flight this is near zero, as no sideways lift is desired.
If you roll the aircraft 90 degrees and maintain it, you can with an alpha near zero and  a sufficiently high beta angle generate sufficient sideways (now directed skywards) lift to maintain level flight, if the shape and size of the fuselage allow this. (This is the knife edge maneuver illustrated by the picture in Peter Kämpfs reply).
Aerobatic aircraft can be designed for this. Some aircraft might be able to maintain altitude momentarily in knife edge, but will be unable to maintain the relatively high airspeed required to do this, and will eventually start descending.

We do that all the time with our radio-controlled airplanes. It's called a knife-edge maneuver. Maintaining altitude is easy provided you have enough power and rudder surface area, but maintaining a straight line (with elevator) is usually very tough.
Not every radio-controlled aircraft can do it though. Usually the planes with small rudder deflection cannot hold altitude if their surface area is small. Aerobatic ones can do it all day along. In fact, an elegant way of coming out of this maneuver is to climb up at the end in that same orientation.
During this maneuver the nose of the airplane will always be a little higher (hence in a pitch up attitude) than the tail. I don't see anyone doing it without pitch up and still maintaining the altitude.

"I don't see anyone doing it without pitch up and still maintaining the altitude." That's because, at least for normal aircraft designs, that isn't possible. Since you're using the combination of thrust and lift from the fuselage to maintain altitude, both of those things require a nose-up attitude for an airplane flying at 90 degrees bank angle. Both the net lift from the fuselage and the lift from the thrust will be zero if you're flying nose-level and 0 AoA. Of course, once you start descending, your AoA isn't zero any more, but you also obviously aren't maintaining altitude.

Not really all that complicated. It all depends on if the specific airframe is designed for such maneuvers and the power plant is robust enough for sustained operation in this mode of flight. MANY aircraft can sustain flight in horizontal flight with the wings 90 degrees to the ground. The Navy's Blue Angels and the USAF's Thunderbirds do this on a daily basis at their airshows. Moving an airfoil to 90 degrees, 180 degrees, 270 degrees, or even through 360 degrees (barrel roll) is accomplished through the wings ailerons. Most aircraft capable of aerobatic maneuvers have trim tabs on ailerons, rudder and elevator to assist in prolonging such maneuvers. Although most light aircraft do not have trim tabs on the rudder and elevator.
I have witnessed a Pilatus Porter (Fairchild) take off near vertical with less than a 40 foot ground roll. Granted it was stripped down and supercharged but it performed as advertised. I think there was a Youtube type video on this out there somewhere at one point. The demonstration was performed by the US Army in the 1970s.

Hello exUSAATController, welcome at Aviation.SE. Please don't use the answer box for follow up questions. Instead you can create a new question and in it refer to this question.

Only if there is a force vector component pointing up.
Model planes tend to have a large rudder which provides lift when turned 90 degrees.  Fighter jets have vectored nozzles that can turn to provide lift in a 90 degree maneuver.
Most passenger airplanes cannot perform such maneuvers.

I'm unsure about your comment on Jets.  If you mean "thrust vectoring" very few fighter jet have it, and it's only capable of creating yaw moments, not 90 degree left.  And if you mean the lift nozels on a Harrier, they also cannot be turned enough to lift a harrier at 90 degrees and, even if they could, they are only on one side of the craft, so the craft would fall over.  Fighters use the side of the craft to create the lift moment for sustained 90 degree flight.  Check the main answer for clarifications...

Yaw in level flight becomes pitch in 90 degree flight.  Lets not be too technical with what does and does not have thrust vectoring.  Point is 'Only if there is a force vector component pointing up' will an aircraft maintain 90 degree flight.

Fair enough.  My only point was that thrust vectoring can't be pointed down to create lift.  When a plane is on it's side, thrust vectoring could be used to keep the nose pitched up, but the body is still what's creating the lift.


text:
How are the glide polar and L/D ratio charts related?
We know from other questions and answers that airplanes and gliders in particular can have their performance described in terms of glide polar and Lift-to-Drag ratio.
As it appears from the images in the first linked answer (included below), the two are connected to each other.
Despite my research I couldn't find a source on how to derive one curve given the other (the polar given the ratio or the ratio given the polar).
Is it possible to do so? I have heard from friends that are glider pilots that the glide polar curve can be described as a parabola, but I haven't found any reference.

L/D ratio

Glide Polar

Images from this question

@PeterKämpf I only changed the tags, not the title, so I plead not guilty :-)

@Pondlife: Right, that was fooot. No problem, enjoyed it.

@fooot: That made me rewrite my answer. The new title needs a fitting answer.

@PeterKämpf We're trying to improve titles and it's good to see it eliciting improved answers as well. Hopefully it doesn't change the actual question too much. Thanks for adding to your answer.

The curves in the top chart are gradients. The bottom chart lists these gradients over flight speed. Say you have in the top chart the y-value L/D = 36 at an x-value of 36 m/s, you do this:

Every point in the bottom diagram can be constructed by drawing a line (red in the example above) from the origin of the coordinate system with the gradient given by the y-value. Where it reaches the corresponding x-value, you get one point of the blue curve in the bottom diagram. You will need to do this for many x-y pairs to get a full polar curve. I used m/s on both axes to make the procedure more transparent.

The parabola is not so bad for a first-order approximation. If we assume that drag is composed of friction drag and induced drag, we can express this as
$$c_D = c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$$
where $c_D$ is the drag coefficient, $c_{D0}$ is the drag coefficient at zero lift (caused mainly by friction drag), $c_L$ is the lift coefficient, $\pi$ is 3.14159…, AR is the aspect ratio of the wing and $\epsilon$ is the Oswald factor (which mainly describes how well the lift is distributed over the span of the wing. Use 0.98 for gliders and 0.7 - 0.8 for other aircraft).
If you plot this, it is indeed a parabola, and it fits with measured drag polars quite well. The model breaks down beyond the upper and lower stall angles of attack when flow separation causes the lift slope to become nonlinear. If you want to re-create the DG plots in your question, you should use the equation above and keep $c_L$ constant at the $c_{L max}$ for plotting, but calculate $c_D$ with the linearly increasing $c_L$, so the induced drag continues to grow even when the wing stalls. This gives a very good approximation even beyond the stall angle of attack.
Otto Lilienthal was the first pioneer of manned flight who measured the lift and drag of airfoils and wings, and he published the results in a polar diagram. That is why we still call these plots polars today, even when we use Carthesian coordinate systems.
To arrive at speeds, you need to add wing loading $\frac{W}{S} = \frac{m\cdot g}{S}$ and air density $\rho$ like this:
$$v = \sqrt{\frac{2\cdot m\cdot g}{\rho\cdot S\cdot c_L}}$$
For the sink speed, things get much easier if we assume that the cosine of the glide path angle $\gamma$ is 1. Then we can write:
$$v_z = v\cdot \frac{c_{D0}}{c_L} + v\cdot \frac{c_L}{\pi\cdot AR\cdot\epsilon}$$
Tabulate $c_L$ in your favorite spreadsheet, compute the speeds like that and plot the result. Make sure you restrict $c_L$ for plotting as explained above! Let me know how close the result is.

thank you! what if we do not assume $cos(\gamma) = 1$? how does the formula look like?

@Federico: Instead of $c_L$ you get $\sqrt{c_L^2 + c_D^2}$ in the denominator. The sink speed is $v_z = v \cdot \frac{c_D}{\sqrt{c_L^2 + c_D^2}}$. Please use the formula for $c_D$ on the top of my answer to expand that further. Typing this in a comment will become impossible to read. Also, the parabolic polar is an approximation, and in order to improve accuracy, maybe the improvement should start there.

It is clear enough, thank you very much!

Thank you for answering a nagging question of mine about why those plots are called polars when they don't normally look like the polar diagrams I'm used to.

Let's look at what exactly is shown by each curve:

The glide ratio curve plots glide ratio (horizontal distance divided by vertical distance) against airspeed.
The polar curve plots vertical speed against airspeed.

The x axis (airspeed) is the same for both plots, but the y axis is different. To convert one curve to the other, we need to convert glide ratio to vertical speed and vice versa.

Note: I'm going to make a slight simplification here and assume that airspeed is the same as horizontal speed. This is not true when climbing or descending. A more accurate answer will require some trigonometry to calculate horizontal speed from airspeed. But the error introduced by this simplification is very small.

Vertical speed is simply airspeed times glide ratio.
Glide ratio is simply vertical speed divided by airspeed.

So, to make one curve out of the other:

To plot the polar curve, take a glide ratio curve and multiply it by the x coordinate (thus converting glide ratios to vertical speeds). Conceptually, as you travel outward on the x axis, you are magnifying the curve by x.
To plot a glide ratio curve, take the polar curve and divide it by the x coordinate (thus converting vertical speeds to glide ratios).

You mentioned parabolas. The polar curve is a "parabola" only in the vaguest sense that it is shaped like a parabola. It is not a precise mathematical parabola. Its exact shape is determined by extremely complicated aerodynamic factors.
All this being said, if your airplane has a published polar curve, use it, instead of deriving your own. Its values were measured and verified during flight test and you're better off using those than something you produced yourself using other data.

The parabola approximation is often used in glide computers due to its simplicity. You can find a number of parameters for several gliders here.


text:
What is the lifespan of a level D simulator?
We have a few interesting questions about the normal ways aircraft end their lives.  What about simulators?  How long do they typically last?  What is the typical reason for retirement?
I am particularly asking about high level simulators used for airliner type ratings.
This question was inspired by discussion of the time taken to reboot a simulator:
Do Flight Simulation Instructors stop the simulator before a simulated crash?
Related questions:

Why are some aircraft's life limited by both cycles and flight hours?
Under what conditions do airliners retire aircraft and sell them to other airlines?
What limits the lifespan of helicopters?
What is the lifespan of commercial airframes (in general)?

Have any advanced simulators outlived the aircraft model they simulate?  Perhaps they can still be operated for a profit if people will pay for simulated time for fun?  I remember seeing the simulator company near me advertising simulator time to non-pilots.

I would assume that simulators are so expensive to operate that if they are ever phased out for reasons other than being worn out (and not being sold), it would still be too expensive for people to do just for fun.

@AnonymousPhysicist, Well, the 737-200 isn't totally retired, but it is extremely rare, and the Delta Flight Museum in Atlanta has a sim for it that's open to the public. Worth every penny :D

Concorde simulator is still preserved in Brooklands museum. FFS are designed for a life of more than 20 years. Over the life there may be software or hardware updates. When the simulator of an old aircraft is decommissioned the parts may be thrown away and you can find them on marketplaces on the internet. It's nothing special from an airline point of view: just a big thing that is used for training

B-52 flight simulators (Weapon System Trainers, a very cool full flight simulator that could integrate with the tanker flight simulators) weren't new when I worked on them in the mid 80s. They were still being used in 2014. And may still be. https://www.minot.af.mil/News/Article-Display/Article/806529/new-innovations-improve-b-52-simulation/

Lifespan of a Level D simulator is: as long as the maintenance costs are justified.
Image source
Maintenance costs of a simulator is according a typical bathtub curve, with the right side of the curve forever climbing up and up. Like with operating and maintaining an old-timer car, as long as spare parts can be purchased it is only a matter of justifying the costs.
New Full Flight Simulators are produced for new aircraft types. As long as an old aircraft type is still flying, there will be pilots that need to be trained on a Level D simulator constructed decades ago. There will be fewer and fewer of the old type simulators around, so training on an oldie may be very expensive indeed.
But spare part availability is the key. The real-time computers, I/O systems and analog electronics of the early 90s are really hard to find nowadays. But even then there is a solution: replace the old simulator sub-systems with modern ones. Host computer, visual, motion, control loading, audio, I/O, Instructor Operator System, weather radar...Not a cheap option, by the time all relevant systems are replaced the upgrade costs are higher than that of a newly constructed sim. But the costs can be spread over several years, with only the most pressing ones tackled year-by-year.
I know of several Level D sims constructed in the early 90s that are still in operation. Indeed the B737-200 in the museum mentioned by @ymb1, there is also one in Jakarta operated by Sriwijaya.
We're upgrading an 1993 Level D sim at the moment. Almost 30 years old, targeted  future use of over two decades...

In some systems/scenarios, the right side curve might not continue to climb up past a certain point: at some (high point), you would likely hit a "ship of Theseus" regime where a constant rate of new parts produces a relatively stable rate of failures, because all of the parts are newer than the whole, and get replaced at some stabilized interval.